All temporary files created by Recital are stored in the directory specified by the environment variable DB_TMPDIR.
In order to have these files stored in memory first create a temporary directory
mkdir /opt/recital/tmp
Then mount the directory with the tmpfs command
mount -t tmpfs -o size=1g recitaltmpfs /usr/recital/tmp
Then change the DB_TMPDIR variable in the recital.conf to point to the newly created temporary directory.